“What could be causing sharp cramps in my vagina?”

Very difficult question. As a general rule the vagina does not cause a lot of pain or cramping. More likely would be 1 of the surrounding structures including the bowels, bladder, uterus. Impossible to know without additional history and physical exam. Possibilities would include uterine cramping but this would generally cycle with your menstrual cycles. Bladder cramping would be less likely in a younger patient such as yourself. Irritable bowel syndrome could cause pain but more likely would be associated with bowel function. Always a chance of infection but again that would take a thorough pelvic exam to determine that. Possibilities might also include endometriosis and that should be discussed with your medical provider. Not likely to represent a dangerous situation but if catching your attention and persisting/progressing should be evaluated.